1. Field of the Invention
The present invention relates to a packaging apparatus for optical interconnection, and more particularly to a packaging apparatus for optical interconnection on an optical PCB, in which an optically active element (such as a semiconductor laser, a photo diode, etc.) is mounted on a printed circuit board (hereinafter, referred to as an “optical PCB”) provided with an optical waveguide.
2. Description of the Related Art
In the simplest structure of packaging apparatus for optical interconnection on an optical PCB, which is well known to those skilled in the art, metal pads and solder bumps are located adjacent to an optical via hole formed through the PCB, and an optically active element is mounted on the PCB by a flip-bonding method.
U.S. Pat. No. 6,512,861, entitled “PACKAGING AND ASSEMBLY METHOD FOR OPTICAL COUPLING,” to Kishore K., Chakravorty, et al., discloses a structure in which a BGA (Ball Grid Array) package, obtained by flip-bonding a surface emitting laser to a BGA substrate is mounted on the printed circuit board. The BGA substrate is provided with a through hole serving as a route for passing an optical signal in order to integrate an optically active element onto a printed circuit board including an optical waveguide.
Another known structure in which a surface emitting laser is bonded to an electrical substrate, is then vertically mounted in a printed circuit board so that an optical signal outputted from the surface emitting laser is directly incident on an optical waveguide of the printed circuit board.
In the simplest structure, in which the optically active element is directly flip-bonded to the printed circuit board, the optically active element has a relatively small size compared to the diameter of the solder balls and the size of the metal pads on the printed circuit board, manufactured by a conventional process, thus causing difficulty in precisely integrating the optically active element onto the printed circuit board.
In the BGA structure, since the BGA substrate is manufactured by a conventional process for manufacturing the printed circuit board, it is difficult to form the through hole at a precise location on the BGA substrate and to mount an optically active element on the BGA substrate. Also, since an optical signal emitted from the surface emitting laser is spread outwardly due to the thickness of the BGA substrate, the BGA package requires a micro lens separately installed on a lower end of the BGA substrate.
In the structure in which the surface emitting laser is vertically installed in the PCB, it is difficult to electrically connect to the surface emitting laser transmitting and receiving chips, which must be exposed through the printed circuit board so as to emit heat.